Add initial Controller to DownloadService

components/download/internal/client_set.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/download/internal/client_set.h"
+
+namespace download {
+
+ClientSet::ClientSet(std::unique_ptr<DownloadClientMap> clients)
+    : clients_(std::move(clients)) {
+  DCHECK(clients_->find(DownloadClient::INVALID) == clients_->end());
+}
+
+ClientSet::~ClientSet() = default;
+
+std::set<DownloadClient> ClientSet::GetRegisteredClients() const {
+  std::set<DownloadClient> clients;
+  for (const auto& it : *clients_) {
+    clients.insert(it.first);
+  }
+
+  return clients;
+}
+
+Client* ClientSet::GetClient(DownloadClient id) const {
+  const auto& it = clients_->find(id);
+  return it == clients_->end() ? nullptr : it->second.get();
+}
+
+}  // namespace download